Improvement of Optical and Thermal Properties for Quantum Dots WLEDs by Controlling Layer Location

Abstract

The inorganic halide perovskite quantum dots (QDs) have been considered as a promising substitute for white light-emitting diodes (WLEDs). In this paper, the green CsPbBr 3 QDs and red K 2 SiF 6 :Mn 4+ (KSF) phosphor were used to fabricate the conversion layers. Because the location of the layers is fundamental to the absorption priority of blue light, the location of KSF and QDs were controlled and the QDs-up type and QDs-down type WLEDs were made. The optical power, luminous efficiency, CCE, and luminous intensity in the middle of QDs-up type are 13.83 mW, 13.54 lm/W, 11.94%, and 2.65 cd, meaning 24.26%, 25.72%, 2.63%, and 23.83% higher than those of QDs-down type, respectively. In addition, the QDs-up type has a lower correlated color temperature (CCT) shift of 734 K and a decreased highest temperature of 56.8 • (51.5% and 14.9% lower). These key property differences indicate that the QDs-up type is more suitable for the application in display and backlight. In order to explore the reasons for these differences, the emission spectra, CCE, reflection rate, absorption rate, and temperature curves of QDs or KSF films were also analyzed, which provided a better understanding of designing package structures. INDEX TERMS Quantum dots WLEDs, optical properties, thermal properties, layer location.

White hairy layer on the Boehmeria nivea leaf—inspiration for reflective coatings

“…As shown in figure 8(a), when excitation light shines through the QD film, part of the light is absorbed by the QDs and down-converted to long-wavelength emission, in our case, namely green emission. Due to the non-scattering property of QD particles and lim- ited thickness of the QD layer, insufficient absorption is always the obstacle to hinder the real application [53,54]. With the electrospinning film as a back reflective film, the excitation light can be recycled before leaving from the lower interface, thus enabling more absorption by the QDs.…”

Synthesis of Highly Photoluminescent All-Inorganic CsPbX3 Nanocrystals via Interfacial Anion Exchange Reactions

“…Perovskite NCs or other quantum dots are generally unstable at high temperatures [34]. Considering such thermal instability of the perovskite NCs and the heat generated by blue LED chips, an effective approach to avoid the temperature effect is to use the remote phosphor configuration, in which the phosphor layer is separated from the LED excitation light source [35,36]. To evaluate the as-synthesized CsPbX 3 NCs for white LED (WLED) applications, the WLEDs, including green CsPbBr 3 NCs film, a red CdSe film, and a blue LED chip, were fabricated.…”

Quantum Dots Electrostatically Adsorbed on the Surface of SiO2 Nanoparticle-Decorated Phosphor Particles for White Light-Emitting Diodes with a Stable Optical Performance

“…After several minutes, phosphor is distributed in a gradient concentration in silicone but QDs are still distributed uniformly. The different distributions of phosphor and QDs change their light-emitting intensity because phosphor situated at the bottom gets more exciting blue light than the QDs. − …”